Liquid filter comprising air vents

ABSTRACT

The invention relates to a liquid filter for motor vehicles, i.e. a fuel filter for an internal combustion engine, comprising an air purging device for the air which is driven out of the filter when there is an increase in the volume of liquid. Said air-purging device comprises a hole having low air resistance and high liquid resistance. A second such device is provided and the two holes are successively arranged in the direction of the air flow.

[0001] The innovation relates to a liquid filter according to the preamble of claim 1.

[0002] A generic filter is known from DE 195 19 352 C2. When it is used, e.g., as a fuel filter for diesel fuel, air bubbles that could be conveyed to the engine are to be avoided, so a venting is provided in the liquid filter for this reason. Through this venting, and in particular through the bore thereby provided which is also termed a vent nozzle, a permanent loss volume flow of fuel results, which is conveyed directly back into the tank together with the air bubbles. In practice, e.g., bores with diameters of 0.7 mm are usual. However, the loss volume flow passing through these comparatively large bores should be as low as possible.

[0003] The object of the innovation is to improve a generic liquid filter so that the loss volume flow is as low as possible with reliable venting, whereby a reliable retention of the venting function is ensured and the production of the liquid filter can be carried out as cost-effectively as possible.

[0004] This object is attained with a liquid filter with the features of claim 1.

[0005] In other words, the innovation proposes connecting two vent nozzles in series, i.e., to provide two bores that are arranged in series in the flow direction of the air bubbles or of the fuel loss flow. An increased resistance for the liquid thus results compared with the use of only one vent nozzle of the same size. When only one vent nozzle is used, this increased resistance could be achieved by a reduced diameter of the bore; however, this can be expensive in terms of manufacturing technology and in addition can involve the risk of the particularly small bore clogging quickly, so that the venting function is no longer performed. The two bores can be advantageously produced according to the present innovation by the manufacturing method hitherto used.

[0006] Partly contradictory objectives are thus achieved: firstly, an easy fabrication, since mandrels can be used in injection mold tools which have the comparatively large diameter of the bore to be produced and which are correspondingly stable and resistant to breakage; secondly, the comparatively large diameter of the bores provides a safeguard against clogging during the operation of the filter, and thirdly, despite the comparatively large diameter of the individual bores, the desired higher flow resistance for the liquid is achieved.

[0007] An expansion chamber can be advantageously provided between the two bores, which chamber features a considerably larger cross section than the two bores. Through this expansion chamber the effect of a bore resulting with a particularly long length is avoided, so that the resistance to clogging of the vent nozzle arrangement is improved and the ease of fabrication facilitated by this, too. In addition, if necessary, the flow resistance can be influenced, namely increased, by means of a flow deflection or swirling within the expansion chamber.

[0008] Advantageously, it can be provided to provide one of the two bores on a removable filter component and the other of the two bores on a fixed filter component. Through this distribution of the bores to fixed and removable components of the filter, it is possible simply and cost-effectively to arrange the two bores in series in the flow direction within the scope of the assembly of the filter which takes place anyway. With a conventional embodiment of a liquid filter such as, e.g., the generic filter, one bore can be provided in the end plate of the filter element and the other bore at the air-vent pipe.

[0009] Naturally, it can be provided to use more than the aforementioned two bores. A kind of “nozzle section,” for instance, can thus be made up of several bores, e.g., of any number of conical and cup-shaped components arranged in series that can be fitted into one another and that each feature the bore in the “cup base” and that can be connected to one another, e.g., swaged, adhered or welded, and whereby the entire nozzle section can be subsequently installed in the filter.

[0010] An exemplary embodiment of the innovation is described in more detail below on the basis of the drawing.

[0011] In general, 1 is thereby used to label a liquid filter shown only in section, which filter is provided as a fuel filter for a vehicle with an internal combustion engine. The liquid filter 1 features a cover 2 that can be screwed onto a filter housing (not shown). After the cover 2 is removed, a filter element 3 can be replaced, whereby this filter element 3 comprises only three components, i.e., a filter medium 4, e.g., in the form of a paper folded filter, and two end plates made of plastic, of which only the upper end plate 5 is shown in the drawing.

[0012] In order to support the filter medium 4 during operation, when it is possibly softened, a support dome 6 is provided in the interior of the filter element 3, on which dome the filter medium 4 can rest during operation of the filter 1. The fuel to be filtered passes from the radial outside to the radial inside through the filter medium 4, there reaches the clean side of the filter 1 and can flow off downwards. An air-vent pipe 7 is provided on this clean side of the filter 1, namely inside the support dome 6, through which air-vent pipe a loss flow constantly flows back into the fuel tank. From the raw side of the filter 1, thus from outside the filter element 3, fuel can pass through a first bore 8, which is provided in the upper end plate 5 of the filter element 3, and subsequently through a second bore 9 that is provided in the upper front wall of the air-vent pipe 7. An expansion chamber 10 is located between the two bores 8 and 9.

[0013] A collar 11 is provided on the upper end plate 5 between the upper end plate 5 and the front end of the air-vent pipe 7, which collar features a sealing contour on its underside where it rests on the air-vent pipe 7, so that a liquid-tight connection of the upper end plate 5 to the air-vent pipe 7 is guaranteed here.

[0014] Unlike the exemplary embodiment shown, more than two bores connected in series can be provided. 

1. Liquid filter for motor vehicles, such as a fuel filter for an internal combustion engine, with a venting arrangement for the air displaced from the filter with increasing liquid volume, whereby the venting arrangement features a bore termed a vent nozzle that features a low resistance to air and a great resistance to liquid, characterized in that two vent nozzles are connected in series, whereby a second such bore (9) is provided and the two bores (8, 9) are arranged in series in the flow direction of the air, and whereby the two bores (8, 9) form an increased resistance to the liquid compared with the use of one vent nozzle with only a single bore of the size featured by one of the two bores (8, 9).
 2. Liquid filter according to claim 1, characterized by an expansion chamber (10) that is arranged between the two bores (8, 9) and features a considerably larger cross section than the two bores (8, 9) such that the two bores (8, 9) are spaced apart to avoid the effect of producing one bore of a particularly long length.
 3. Liquid filter according to claim 1 or 2, characterized in that one bore (8) is provided on a removable filter element (3), such as on an end plate (5) of this filter element (3), and the other bore (9) is provided on a fixed filter component, such as on a support dome (6), which supports the filter medium (4) of a ring-shaped filter element (3) inside.
 4. Liquid filter according to one of the preceding claims, characterized in that more than two bores (8, 9) in series are provided. 